Automotive climate control systems typically have a door, or damper, for regulating air flow from a conditioning element, such as a heater or air conditioner, through a duct to a desired area, such as a passenger compartment. Ideally, the door completely blocks air flow through the duct when closed. To that end, a pliable seal is typically placed on the door to achieve a tight fit with a mating surface.
Heretofore, various seals have been used for this purpose. One common seal, often referred to as a pressure sensitive adhesive (PSA) seal, consists of a urethane material having an adhesive strip on one side. The seal is placed on the door with the adhesive strip facing downwards and pressure is applied to "stick" the seal to the door. Although acceptable for many applications, urethane PSA seals have some drawbacks which make them undesirable for an automobile climate control system. For example, urethanes are an open-cell material able to collect moisture in which odor producing bacteria may grow. In addition, the PSA seals are packaged onto a cardboard base with a plastic film covering the adhesive side which must be removed and discarded before applying the seal to the door. Such a step increases the labor requirements to apply the seal while also producing waste, usually non-recyclable, in the form of the plastic film and cardboard base. Further, the "peel and stick" method used to apply the PSA seals is not consistently repeatable leading to inadequately applied seals.
Other methods for applying seals or gaskets to substrates are described in U.S. Pat. No. 5,382,397 (Turner, Jr.) and U.S. Pat. No. 5,164,136 (Comert et al.). In the Turner, Jr. patent, a controlled amount of liquid sealant material is metered from a bulk reservoir to a seam, such as along joined automobile body panels. The sealant material has a closed cell foam structure with a multitude of fine cells containing gas. Apparatus for mixing and metering an even flow of material is also described. The patent does not describe how to use the apparatus for applying the material to a substrate enclosed within a mold.
In the Comert et al. patent, one method disclosed consists of injecting a gasket material into a mold containing a substrate to form a gasket thereon, removing the substrate from the mold, and exposing the part to moisture to cure the material. The gasket material consists of a moisture curable semi-IPN (interpenetrating polymer network) made by blending at least two components, one being a primary polymer with isocyante end groups, the other being a non-crosslinked elastomer. Use of a primary polymer with isocyante end groups may result in cyanide by-products which must be carefully handled to avoid harmful consequences. In addition, the method requires exposure to moisture to effect curing of the material, and the blended material must therefore be kept from moisture until curing is desired. Further, while injection into a mold may work with the blended material described in the Comert et al. patent, it has been found not to work with other high-viscosity sealant materials due to back pressure in the mold cavity. Injection methods result in incomplete filling of the mold channel as well as a lower than desired seal durometer due to separation of the gas from the material.
There thus exists a need for applying a recyclable, closed-cell, high viscosity material seal to a substrate to provide a pliable seal in a method which does not require excessive manufacturing steps and which does not produce undesirable by-products.